Field of the Invention
The present invention relates to a vibration detection apparatus and a vibration detection method, and an image capturing apparatus.
Description of the Related Art
Panning shooting is one camera shooting method. The panning shooting is a method in which shooting is performed by following a moving subject with a camera, and in general, the shooting is performed with a slow shutter speed so as to generate a dynamic feeling of the subject.
However, experience is needed in shooting a subject (train moving at 60 km/h, for example) while panning the camera so as to appropriately follow the subject at a slow shutter speed ( 1/30 s, for example). In particular, it is difficult for a beginner to adjust the panning speed of the camera to the speed of the subject during an exposure period at a slow shutter speed, and therefore, the panning shooting is a difficult shooting method.
In Japanese Patent Laid-Open No. 2006-317848, a method is disclosed in which the difference between a subject speed and a panning speed of the camera is detected, and the shift amount corresponding to the difference is corrected using an image stabilization function in order to easily realize the panning shooting. In this method, an angular velocity sensor in the camera detects, immediately before shooting, the angular velocity with respect to the panning (or tilting) of the camera following the subject. A moving amount of a main subject image on an imaging plane is detected at the same time. The angular velocity of the subject is calculated from the detected panning speed and the moving amount of the subject image on the imaging plane. Then, an image stabilization operation is performed during exposure in accordance with the calculated difference amount between the angular velocity of the main subject and the output of the angular velocity sensor in the camera. Accordingly, the difference (subject vibration amount) between the main subject speed and the panning speed of the camera, and the camera shake amount are corrected, and thus the image blur of the main subject that is the target of the panning shooting can be restricted.
Also, a method in which the motion of an image is detected using a motion vector is known as a technique for detecting a movement in a screen, and a correlation method based on a correlation operation, a block matching method, and the like are known as a detection method of the motion vector. In the block matching method, an image signal that is input is divided into a plurality of block regions each having an appropriate size, and differences from pixels in a certain range of the previous frame is calculated for each block. Then, a block in the previous frame with which the sum of absolute values of the differences is the minimum is searched for. The relative shift, between frames, of each block and the corresponding searched block represents the motion vector of the block.
Also, in Japanese Patent Laid-Open No. 2015-161730, a method for improving detection accuracy of a subject vector is disclosed in which vectors in a frame that are detected from motion vectors and an angular velocity sensor or the like that detects vibration applied to the camera are both utilized. In this method, the vectors in the frame are compared with an on-imaging plane moving amount on an imaging plane that has been converted from the angular velocity, and vectors in the vicinity of the on-imaging plane moving amount are determined as background vectors, and vectors that are separate from the on-imaging plane moving amount by an amount greater than or equal to a certain amount are determined as the subject vectors.
However, in a shooting scene such as that of taking a panning shot of a slow moving subject, because the panning speed at the time of following the subject is low, the output of the angular velocity becomes small, and the difference between the subject vectors and the background vectors decreases. As a result, almost all the vectors are erroneously detected as the subject vectors, and accurate detection of the subject vectors cannot be performed.